Antipsychotic agents are described in U.S. Pat. Nos. 4,605,655 and 4,994,460, issued Aug. 12, 1986 and Feb. 19, 1991, respectively. Of these agents, a compound identified as BMY 14,802 having the structure ##STR4## is preferred. The R(+) isomer of BMY 14,802 and the other compounds disclosed in these patents are believed to be more active, although S isomers are also useful antipsychotic agents. No enzymatic or microbial preparations of these compounds is known, and chemical stereoselective preparation is difficult. A need exists, therefore, for a stereoselective preparation of these compounds in high yield and high stereoisomeric purity.